It sometimes depends if you are relying on first party documentation or not. I have used systems with full and proper documentation and searching for an error

It sometimes depends if you are relying on first party documentation or not. I have used systems with full and proper documentation and searching for an error code will give an exact match and as much detail as I want, sometimes in offline documentation and sometimes online. While error messages often cause problems on Google. For your example, try selecting it and searching 'account_deactivated' in Google. Showing results for account deactivated Search instead for account_deactivated Click that 'search instead' link. Google clearly ignores the underscore in the results so it's not doing what it says it will. The way around this is to quote the text but IMO searching something like '<productname> error 0x5678' is clear, reliable, and easy. These will often be paired with a token like your example anyway, such as IRQL_NOT_LESS_OR_EQUAL, so you get both.